Optimizing a Remote-based Physical Activity Intervention for Adults with Total Knee Replacement - Over 4 million adults are living with a total knee replacement (TKR); however, most do not achieve recommended physical activity levels. To date, physical activity interventions for adults with TKR have primarily been intensive, in-person, and costly interventions. However, given the barriers associated with these intensive programs (e.g., time and travel burdens), scalable approaches for increasing physical activity in this population are needed to address high rates of inactivity, and related risk of chronic disease and mortality. Fully- automated Internet programs have potential for increasing physical activity but have rarely been tested in adults with TKR. Further, it is unknown whether this intervention approach can be scalable and effective in this population or whether additional enhancements to the program are needed. We propose to use the Multiphase Optimization Strategy (MOST) framework to identify the optimal intervention components within a scalable, internet-based physical activity program for adults who are ≥12 months post-TKR. Participants will be recruited nationwide to participate, and all will receive the core Energize! Exercise Program, a 6-month fully automated program. Energize! provides a platform for participants to plan and report exercise daily, watch and complete behavioral video lessons and related homework assignments, and receive brief automated feedback on activity levels. In addition to Energize!, participants will be randomized to receive 0-4 non-automated supplemental components, which were selected based upon prior research and guided by the Self-Determination Theory (SDT) and Supportive Accountability: 1) phone coaching, 2) progress reports sent to physicians/surgeons, 3) tailored modules specific to adults with TKR, and 4) individualized human feedback (delivered electronically) on submitted homework assignments. The primary aim is to identify which supplemental intervention components contribute to the greatest increases in physical activity (total moderate-to-vigorous intensity physical activity [MVPA] and percent meeting guidelines [≥150 min/week of MVPA]) at 6 and 12 months. Secondary aims include assessing the effect of the intervention components on pain and physical function and examining how the core and supplemental intervention components mediate changes in physical activity via targeted mechanisms: program adherence, SDT targets (autonomy, competence, relatedness), and supportive accountability. The overarching goal of this study is to build an optimized physical activity intervention for adults with TKR using the supplemental non-automated components that were found to contribute significantly to increases in physical activity. Once developed, this optimized intervention can be fully tested in a future trial. Study findings have the potential to impact clinical practice, as this would represent a translatable model that could be scaled within healthcare systems for adults with TKR.
